To ensure that each scene of a motion picture has the same basic lighting, a grayscale chart is typically recorded on one or more frames of film or video tape at the beginning of the scene by the camera recording the scene. A grayscale chart (or gamma chart) is a commonly known quality control element having a range of calibrated neutral density (i.e., gray) reflectance values from black to white. These known neutral density reflectances are used during the transfer process to enable film-makers to visually assess and maintain proper color balance, brightness and contrast while also compensating for effects that variables in film stock, film age, and lighting have on the color images.
Images from film may be transferred to video tape or to computer-readable media to be used, for example, in an editing system, such as the Avid Symphony nonlinear editing (NLE) system, where they may be digitally edited. An editor uses the NLE system to create a composition including segments from a digitized version of the film. The data that represents the composition commonly is referred to as xe2x80x9cmeta-dataxe2x80x9d and may be stored in a data file or in a database. The digital editing system may provide, for example, a cut list that specifies how the negative may be cut to produce the motion picture. Using the cut list, the negative is then cut and rearranged in the correct order. This negative becomes what is commonly known as the xe2x80x9cmaster negative.xe2x80x9d The master negative is used to create a final color copy of the motion picture. The final color copy may be used by a transfer device to transfer images from the final color copy to a distribution medium.
After or during transfer of images from film, color correcting is typically performed. This color correction is typically performed by an expert called a colorist. Color correction may be performed using several different devices during the production of a motion picture. For instance, color correction may be performed when film is transferred to video tape or to computer readable media using a telecine. Color correction also may be performed when the film is transferred to various other media such as digital versatile disk (DVD), television signals format (e.g., PAL and NTSC), high definition television (HDTV) format, and the like. For each type of transfer, a different color correcting device may be used. Currently, various color correcting devices and processes are used on an ad hoc basis and operate in isolation.
Each color correction device has it own characteristics, settings and calibrations so that color correction settings on one color correction device do not create the same result on a different device. To overcome this drawback, information related to the representation of known color standards on both devices may be captured and used to cross-correlate color correction information from one device to color correction information to be used by another device.
In one embodiment, a method which duplicates the effective degree and range of color correction on a second color correction device for a still or moving image previously color corrected on a first color correction device is disclosed. The method of this embodiment includes steps of nulling, on the first color correction device, at least one color corresponding to at least one know color in an image containing a known standard using the first device to obtain a primary offset value on at least one color axis, retaining the control offset in a manner associated with the image, and performing further color correction corrections with the first device on a series of subsequent images, and retaining information related to the further color corrections in a manner associated with the subsequent images. The method of this embodiment also includes steps of nulling, on the second color correction device the at least one color corresponding to that at least one known color in the image containing the known standard using the second device to obtain a secondary offset value on the at least one color axis, receiving the offset on the at least one color axis obtained on the first device, and using the primary and secondary offsets to derive a correlation mapping of color correction control information such that color correction control information may be accurately communicated from the first color correction device to the second color correction device.
In one embodiment, a method duplicating color correction on a second device for an image in a motion picture corrected on a first device is disclosed. The method of this embodiment includes steps of nulling at least one color corresponding to at least one known color in an image containing a known standard using the first device to obtain an offset on at least one color axis, retaining the offset in a manner associated with the motion picture and performing color correction using the first device and retaining information about the color correction. The method of this embodiment also includes steps of nulling at least one color corresponding to the at least one known color in the image containing the known standard using the second device to obtain an offset on the at least one color axis, receiving the offset on the at least one color axis obtained on a first device and using the offsets from the first and second devices to generate a mapping of color correction information from the first device to color correction information for the second device.
In another embodiment, a method of performing color corrections on a motion picture using a color correcting device after color correction operations have been performed on a remote color correction device such that the color corrections conducted using the color correcting device are substantially the same as those performed on the remote color correcting device is disclosed. The method of this embodiment includes a step of receiving the results of a null test performed on the remote device on at least one color corresponding to at least one known color in an image of a known standard. The results may be received as at least one offset on at least one color axis. The method of this embodiment also includes steps of nulling, on the color correcting device, at least one color corresponding to the at least one known color in the image of the known standard to obtain an offset on the at least one color axis and using the offsets from the remote device and the color correcting device to generate a mapping of color correction information from the remote device to color correction information for the color correcting device.
In another embodiment, a method for maintaining color correction information for an image in a motion picture corrected on a first device is disclosed. The method of this embodiment includes steps of nulling at least one color corresponding to at least one known color in an image containing a known standard using the first device to obtain an offset on at least one color axis, retaining the offset in a manner associated with the motion picture and performing color correction using the first device and retaining information about the color correction in a manner associated with the motion picture.
In another embodiment, a motion picture product produced by a process is disclosed. The motion picture product of this embodiment is produced by nulling at least one color corresponding to at least one known color in an image containing a known standard using a first device to obtain a first offset on at least one color axis, retaining the first offset in a manner associated with the motion picture and performing color correction using the first device and retaining information about the color correction in a manner associated with the motion picture. In another embodiment, a color correcting device is disclosed. The color correcting device of this embodiment includes means for receiving color correction information from a remote color correcting device and means for performing color correction.